CAZAC Sequence Grouping for Wireless Resource Allocation
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Solution Overview
Problem
Conventional radio communication systems face a shortage of orthogonal signal sequences for code division multiplexing as the number of radio communication apparatuses increases, leading to reduced throughput and inefficient use of radio resources, particularly with the rise of Machine Type Communication (MTC) terminals that transmit smaller amounts of data intermittently.
Innovation Solution
The system classifies radio communication apparatuses into groups and assigns different CAZAC sequences and shift amounts to each group, allowing for quasi-orthogonal signal sequences to be used, thereby increasing the number of assignable signal sequences and reducing interference between groups, even when there are a large number of apparatuses in a cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If orthogonal signal sequences obtained by cyclic shifts of a single CAZAC sequence are used for code division multiplexing, then interference between signals is prevented, but the number of assignable signal sequences is limited when the number of radio communication apparatuses increases
Solution Approach 1:
The invention segments the signal sequence resource by dividing MTC terminals into multiple groups and assigning different CAZAC sequences to each group. Within each group, cyclic shifts provide orthogonal sequences, while between groups, different base CAZAC sequences are used. This segmentation resolves the contradiction by multiplying the total number of assignable sequences across groups while maintaining orthogonality within each segment.
Solution Approach 2:
The invention adds a new dimension to signal sequence allocation by introducing group-based CAZAC sequence selection in addition to cyclic shift allocation. Instead of only varying cyclic shift amounts within a single CAZAC sequence, the system now varies both the base CAZAC sequence (different dimensions) and cyclic shift amounts, effectively expanding the resource space from one dimension to two dimensions.
2Productivity
If the number of signal sequences for code division multiplexing is increased to support more radio communication apparatuses, then the number of MTC terminals that can transmit data increases, but interference between non-orthogonal sequences may occur
Solution Approach 1:
By segmenting MTC terminals into multiple groups and assigning different CAZAC sequences to each group, the invention ensures that sequences within each group remain orthogonal (no interference), while the segmentation itself reduces inter-group interference through frequency resource allocation. This allows more terminals to transmit simultaneously without significant interference.
Solution Approach 2:
The invention applies local quality by ensuring perfect orthogonality within each group (local region) while accepting quasi-orthogonality between groups. Each group's signal sequences are optimized for zero interference among its members, and frequency resource allocation further reduces inter-group interference, achieving local quality control of interference.
3Ease of operation
If a dedicated uplink control channel is provided for MTC terminals in addition to conventional uplink control channel, then MTC terminals can transmit data autonomously, but radio resource usage efficiency decreases
Solution Approach 1:
The invention merges MTC terminal transmissions with conventional uplink control channels by allowing MTC terminals to use the same physical uplink control channel (PUCCH) resources as conventional terminals. Through code division multiplexing with group-specific CAZAC sequences, both MTC and conventional terminals share the same channel, eliminating the need for separate dedicated channels and improving radio resource efficiency.
Data Source
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AI summary
The number of radio communication apparatuses allowed to transmit data on a certain channel is increased. A base station (10) classifies at least some of radio communication apparatuses (21 through 25) belonging to the same cell into a plurality of groups. The base station (10) assigns to a first group a signal sequence (31) that is orthogonal to a signal sequence obtained by a cyclic shift thereof, and assigns to a second group a signal sequence (33) that is orthogonal to a signal sequence obtained by a cyclic shift thereof and that is different from the signal sequence (31) and from the signal sequence obtained by a cyclic shift of the signal sequence (31). The radio communication apparatus (21, 22) belonging to the first group performs spread modulation on data using the signal sequence (31) or a signal sequence (32) obtained by a cyclic shift of the signal sequence (31). The radio communication apparatus (23, 24) belonging to the second group performs spread modulation on data using the signal sequence (33) or a signal sequence (34) obtained by a cyclic shift of the signal sequence (33).